Hydraulic control system



May 7, 1968 '0. J. PARQUET HYDRAULIC, CONTROL SY STEM Filed Sept. 10,1965 I i l i I 34 K 38 c 74 Si 46 aeJ IZ 48 I 50% 52 INVEN R. D. J.PAROU United States Patent 3,381,587 HYDRAULIC CONTROL SYSTEM Donald J.Parquet, Dike, Iowa, assignor to Deere & Company, Moline, Ill., acorporation of Delaware Filed Sept. 10, 1965, Ser. No. 486,331 1 Claim.(Cl. 91-420) ABSTRACT OF THE DISCLOSURE A hydraulic system forcontrolling a two-way hydraulic cylinder and including a pair ofnormally closed check valves for preventing the return of fluid fromeither side of the cylinder, a pair of opposite coaxial pilot pistonsactuatable to respectively open the check valves, and a control valvefor porting pressurized fluid to either side of the cylinder and to thepilot pistons to open the check valve and dump the unpressurized side atthe cylinder, or for porting pressure only to the pilot pistons to openboth check valves, dumping both sides of the cylinder.

This invention relates to a hydraulic control system and moreparticularly to an improved hydraulic control system havinghydraulically actuated check valves for interrupting the return of fluidfrom a pressure actuated motor.

The improved control system has particular utility on a tractor forcontrolling a two-way hydraulic cylinder which positions aground-working implement or the like. It is known to provide checkvalves in such a system to prevent the flow of fluid from thepressurized side of the cylinder in order that the position of theloaded cylinder may be maintained. It is also known to providehydraulically actuated pistons which unseat the check valves to permitthe exhaust of either end of the cylinder.

In the operation of certain ground-working implements, such as scrapersor the like, in addition to the normal raise and lower positions of thetwo-way cylinder wherein alternate ends of the cylinder are pressurized,it is desirable to have another position in which both ends of thecylinder are exhausted for free floating movement of the implement.However, previous systems, utilizing hydraulically controlled checkvalves, have not provided for such a float position, the hydraulicallyactuated piston or pistons, which control the check valves, beingdesigned to actuate only one check valve at a time, permitting theexhaust of only one end of the cylinder.

According to the present invention, there is provided a novel controlvalve assembly, having hydraulically actuated check valves to maintainthe position of the loaded cylinder, and also having means forsimultaneously opening both check valves to permit floating movement ofthe cylinder.

A more specific object is to provide such a control valve assembly withhydraulically actuated piston means which open alternate check valves topermit exhaust of either end of a hydraulic cylinder or willsimultaneously open both check valves to provide floating movement ofthe cylinder, and further to provide such piston means in the form oftwo coaxial pistons which can be actuated in unison in either directionto alternately open the check valves, or split and actuated in oppositedirections to simultaneously open both check valves.

Another object is to provide such a control valve assembly which is ofsimple and compact construction, easy to manufacture and maintain.

These and other objects will become apparent in the following detaileddescription and accompanying drawing wherein the sole figure is acombined sectional and schematic view of the hydraulic system, showingthe check valve portion of the control valve assembly in section, andschematically showing the remainder of the system, the control valveassembly being shown in a neutral condition.

The hydraulic system includes a control valve assembly, indicated in itsentirety by the numeral 10, and including a body 12, part of which isshown in section. The body 12 has an inlet port 14 communicating with asource of fluid pressure 16 via a conduit 18 and an exhaust port 20communicating with a reservoir 22 via a conduit 24, fluid from thereservoir 22 being supplied to the fluid pressure source 16 through aconduit 26.

A hydraulic motor 28, in the form of a double acting hydraulic cylinderor ram, includes a cylinder 30 and a piston 32 movable within thecylinder in response to a pressure differential between the oppositeends 34 and 36 of the cylinder. One end 34 of the cylinder is connectedto a first motor outlet passage 38 in the body 12 by a conduit 40, andthe other end 36 of the cylinder is connected to a second motor outletpassage 42 in the body 12 by a conduit 44.

A cylindrical bore 46 extends through the body 12 and is transverselyintersected by the motor outlet passages 38 and 42. Three valve passages48, 50, and 52 communicate with the bore 46 between the motor outletpassages 38 and 42, the passages 48 and 38 and the portion of the bore46 between said passages, forming a first passage means through thevalve body 12, and the passages 52 and 42, and the portion of the bore46 between said passages, forming a second passage means through thebody 12.

A pair of cylindrical valve seats 58 and 60 are respectively mounted inthe bore 46 between the passages 48 and 38 and between the passages 52and 42, the valve seats 58 and 60 having axial orifices 62 and 64respectively. The opposite ends of the bore 46 are closed by a pair ofcaps 66 and 68, and the orifices 62 and 64 are respectively closable byspherical check valves 70 and 72 biased against the respective valveseats 58 and 60 by compression springs 74 and 76, the spring 74 actingbetween the cap 66 and the valve 70, and the spring 76 acting betweenthe cap 68 and the valve 72. The valves 70 and 72 are unseated againstthe bias of the springs 74- and 76 when they are subjected to fluidpressure from the passages 48 and 52 respectively and normally preventthe return of fluid from the passages 38 and 42. The movement of thevalves 70 and 72 is limited by axial projections 78 and 80 on therespective caps 66 and 68.

A pair of pistons 82 and 84 are slidable in the bore 46 between thevalves 70 and 72, the pistons having opposite faces 86 and 88 and axialshaft portions 90 and 92 substantially smaller in diameters than theorifices 62 and 64, the terminal ends 94 and 96 of the shaft portions 90and 92 respectively extending through the orifices 62 and 64 and toengage the valves 70 and 72.

A spool type control valve 98, shown schematically in the drawing, isaxially shiftable via an actuating means 99 into four alternatepositions, establishing ditferent connections between the inlet 14 andthe exhaust port 20 and the passages 48, 50 and 52.

In operation, when the valve 98 is in neutral position, as shown in thedrawing, the inlet 14 is blocked and the passages 48, 50 and 52 areconnected to the exhaust port 20 and consequently to the reservoir 22.Since there is no fluid pressure in passages 48, 50, or 52, no force isexerted on either piston 82 or 84, and the springs 74 and 76 maintainthe valves 70 and 72 in a closed position, preventing the flow of fluidfrom either end of the cylinder 30.

When the valve 98 is moved to its raise portion, to the right in thedrawing, the inlet port 14 is connected to the passage 48, the passage50 is blocked, and the passage 52 is connected to the exhaust port 20.The pressure in the passage 48 opens the valve 70 against the bias ofthe 3 spring 74, supplying fluid under pressure to the lower end 34 ofthe cylinder 30 via the outlet passage 38 and the conduit 40. Thepressure in the passage 48 also exerts a force on the piston 82, movingthe pistons 82 and 84 in unison toward the valve 72, to the right in thedrawing, the end 96 of the piston 84 engaging and unseating the valve 72against the bias of the spring 76, permitting the exhaust of fluid fromthe upper end 36 of the cylinder 30 via the conduit 44, the passage 42,the orifice 64, the passage 52, and the valve 98.

When the valve 98 is moved to its lower position, to the left in thedrawing, the inlet port 14 is connected to the passage 52, the passage50 is blocked, and the passage 48 is connected to the exhaust port 20,reversing the previous condition. The pressure in the passage 52 movesthe pistons 84 and 82 in unison, to the left in the drawing, to unseatthe valve 70, permitting the exhaust of the lower end 34 of the cylinder30, the pressure also unseating the valve 72 and pressurizing the upperend 36 of the cylinder 30.

The float position of the valve 98 is obtained by moving the valve 98 toits extreme position, to the left in the drawing, connecting the inletport 14 to the passage 50 and connecting the passages 48 and 52 to theexhaust port 20. The pressure in the passage 50 exerts opposite forceson the opposite piston faces 86 and 88, moving the pistons 82 and 84 inopposite directions to unseat both check valves 70 and 72 and permit thereturn of the fluid from both ends 34- and 36 of the cylinder 30. Sinceboth ends of the cylinder 30 are connected to exhaust, the piston 32 isfree to move in either direction, providing the desired floating action.

Other features and advantages of the present invention will readilyoccur to those skilled in the art, as will many modifications andalterations in the preferred embodiment of the invention describedherein, all of which may be achieved without departing from the spiritand the scope of the invention.

What is claimed is:

1. A hydraulic control system comprising: a source of fluid pressureincluding an associated reservoir; a reversible hydraulic motor havingalternate inlets; a valve body having an elongated bore; first, second,third, fourth, and fifth passages in the valve body respectivelycommunicating with the bore at axially spaced intervals in numericalorder; means respectively connecting the first and the fifth passages tothe alternate motor inlets; a first check valve means mounted in thebore between the first and second passages and biased toward a closedposition wherein it blocks the flow of fluid from the first passage tothe second passage; 9. second check valve means mounted in the borebetween the fourth and fifth passages and biased toward a closedposition wherein it blocks the flow of fluid from the fifth passage tothe fourth passage; a first axially shiftable pilot piston normallypositioned in the bore between the second and third passages; a secondaxially shiftable pilot piston normally positioned in the bore betweenthe third and fourth passages, the pistons moving in unison toward andopening the second check valve means in response to pressurization ofthe second passage, moving in unison toward and opening the first checkvalve means in response to pressurization of the fourth passage, andmoving in opposite directions to open both check valve means in responseto pressurization of the third passage; and a control valve meansshiftable into a first position wherein it connects the third passage tothe reservoir only, a second position wherein it connects the secondpassage only to the fluid pressure source and the fourth passage to thereservoir, a third position wherein it connects the fourth passage onlyto the fluid pressure sourceand the second passage to the reservoir, anda fourth position wherein it connects the third passage only to thefluid pressure source and the second and fourth passages to thereservoir.

References Cited UNITED STATES PATENTS 2,572,705 10/1951 Edman 91-4642,670,713 3/1954 Jirsa 91-20 2,691,964 10/1954 Stickney 91-426 2,830,5614/ 1958 Lindstrom 91-420 2,959,190 11/1960 Barnes et al. 91-4413,223,104 12/1965 Cox et al 137-62562 3,273,467 9/1966 Allen 91-4120MARTIN P. SCHWADRON, Primary Examiner.

B. L. ADAMS, Assistant Examiner.

